The present invention relates to the field of electrical components, and its application is the structural development of encapsulated spark gaps used to divert overvoltages. These types of spark gaps are used, in particular, in combination with gas-filled overvoltage surge arresters, the encapsulated spark gap being electrically shunt-connected to the gas-filled overvoltage surge arrester and designed as a rule as a spark gap in air.
In the case of an encapsulated spark gap for diverting overvoltages, two circular-shaped, copper-containing electrodes mutually oppose each other and are insulated from one another by means of special range spacers, as well as through the interposition of a thin insulating layer of mica, glass or ceramic. The insulating layer is provided with a circular recess in the area of the mutually opposing electrode surfaces, so that an air gap or a gas gap exists between the electrodes. The two electrodes, whose electrode surfaces are coated with graphite or carbon, are joined to one another so as to be hermetically sealed in the outer area. For this purpose, inter alia, a tubular insulator consisting of ceramic, glass or plastic can be used, which is connected in a vacuum-tight manner with the external surface areas of the electrodes (see U.S. Pat. No. 3,898,533, FIG. 3).
A non-encapsulated spark gap has been used in combination with a gas-filled overvoltage surge arrester in the case of which two electrodes abut on both sides of a ceramic disk having multiple punched holes. One of these electrodes is provided with knob-type elevations, which engage into the holes in the ceramic disk. The actual spark gap in air is formed in each case by one knob and the flat counter-electrode (see U.S. Pat. No. 4,366,412). For such spark gaps in air, a mica film has been used having multiple punched holes as a range spacer for the two electrodes (see U.S. Pat. No. 5,142,434).
Finally an arrangement may be used for a gas-filled triple-electrode overvoltage surge arrester, which consists of a central electrode, two hollow-cylindrical ceramic insulators, and two frontally arranged end electrodes, in the case of which a spark gap in air is allocated to each end electrode. This likewise non-encapsulated spark gap in air is formed by means of an end of a metal spring clip top that is arranged with clearance from the end electrode. The metal clip is secured to the central electrode. The required clearance from the end electrode is observed by means of a polyurethane-resin coating. It is applied as a very thin coating to the sharp edges and corners of the two ends of the metal clip (see U.S. Pat. No. 4,912,592).
In the manufacturing of gas-filled overvoltage surge arresters having a tubular insulator of glass, it is generally known to use dish-type electrodes, which are provided with a collar-shaped rim and consist of a nickel-iron or rather a nickel-iron-cobalt alloy, and to join these electrodes to the glass insulator by fusing the ends of the glass insulator in a vacuum-tight manner (see German Patent Document No. 19 51 601 and GB Patent No. 1,280,938).